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How to spot fake pound coin

Blunders and Mistakes of Science and Engineering

This page will document mistakes which are the result of misapplication or ignorance of science and engineering principles. Readers are invited to send us more of this kind of thing, or to provide additional information about the ones already here.

Faulty Vision.

Diagrams purporting to explain how the eye works are often defective, even in textbooks. But this example, from p. 16 of the special 2006 issue "Secrets of the Senses" put out by Scientific American is the most screwed-up I've ever seen (so far). Hardly anything about the ray paths is correct. It shows no deviation in direction of rays at the cornea (which actually causes most of the refraction in real eyes). It has rays devating much too much at the lens, so much that they cross within the lens.

Even worse, one of those rays mysteriously changes direction near the center of the eyelens! The other ray is nearly, but not quite straight there. Apparently the "secrets of the visual sense organ" are still a mystery to the artist and to the editorial staff of the magazine.

The Scientific American once was a good, reliable science magazine. But in recent years it, and other magazines, seem to be pitched at the lowest common denominator of science literacy.

You can read more about this at my science misconceptions page.

Don't judge a book by its cover.

This book cover is from the paperback edition of The Birth of a New Physics by I. Bernard Cohen (Doubleday, 1960). The diagram on the cover is striking, but on closer inspection, one must ask "What's wrong with this picture?"

Clearly it is meant to illustrate Newton's law of gravitation, represented by the equation in the white space below. The symbol D is the distance between the centers of the black spheres, labeled m and m'. But what do the blue and red arrows represent?

They can't be forces, for the mutual forces of attraction acting on the spheres must always be equal size and oppositely directed vectors as required by Newton's third law. Could they be accelerations? No, for the acceleration of the smaller ball is larger than the acceleration of the larger one, the accelerations being in inverse proportion to the masses, satisfying Newton's second law. In short, this artwork fails on several levels, misrepresenting the physics it is supposed to illustrate.

Most likely Prof. Cohen never saw the cover art before the publisher had printed thousands of copies. As one of my colleagues noted, "What can you expect? Its cover price is only 95 cents." I treasure this copy, not only for its excellent contents, but for the cover, which can be used to test whether physics students can spot what's wrong with it.

The little gears that couldn't.

The British do have a sense of humour. Why else would they issue this gold and silver two-pound coin to honor the advance of British industry?

The artistic designer has used a circle of gears of different sizes in an interlocked array. There are 19 gears. Even if they were sized properly, an odd number of gears meshing around a circle couldn't possibly turn. The reason is simple; each gear turns its neighbor in the opposite direction.

How about an even number of gears meshed around a circle? Contrary to one's intuition, such a system will turn freely no matter what the gear

sizes or number of teeth, provided the gear teeth were cut according to good engineering standards. But, even then, the gears wouldn't be doing anything useful. Something like a dog chasing its tail.

One hopes British industry is on the move, even if these gears aren't. Does anyone out there have more documentation on this incident, perhaps public and press reaction, lame excuses by the folks responsible, scientists' reactions? Send all such material to the address below.

The coin was introduced in 1997, to be phased into use gradually. You can read more about it at the Tax Free Gold website.

This is a handsome coin, the first bimetallic coin in British coinage. The inner disc is made of cupro-nickel, while the outer ring is made of nickel-brass. (A collector's version in gold and white gold was also made.) One side has the Queen's profile. The side shown above has a design in the center depicting a chariot wheel. Around this are the gridlocked gears, then a printed circuit, and a pattern which represents the internet. On the milled edge is part of Newton's quote "Standing on the Shoulders of Giants." This is appropriate, since Newton introduced milled coinage in England when he was director of the Mint.

Apparently no one informed the British Mint of this goof before the 2002 coin was issued with the same locked gear design. A 2003 coin had a new design, with the gears replaced by a picture of the structure of DNA, and the edge of the coin then read "Deoxyribonucleic Acid". (Alas, poor Newton; you have been displaced by a molecule.) But then some 2004 coins returned to the gear design. Perhaps someone at the mint does have a sense of humour.

Here's a 2007 update from Darren Dowling in England:

I like to make my students question things and we were discussing gears the other day while learning about loci in a GCSE class. I pointed out the 'error' on the two pound coin and they asked why they did it and why they didn't check first.

So I emailed the Royal Mint and received:

Dear Mr Dowling

Thank you for your recent enquiry respecting the 'technology' design on the reverse of the two-pound coin.

The idea behind the design is to represent the development of technology through the ages but it is not directed at doing this in a literal way. The artist wanted to convey this theme symbolically and so the number of cogs in one of the rings of the design was not a key consideration in his mind.

Your observation is correct and you are not the first person to notice that the number of cogs means the gearing would not strictly speaking work in reality. We would, however, wish to emphasise that this is a coin design symbolic of the development of technology and its success lies in visually representing a complex idea in an interesting and succinct fashion.

Best Regards

Evelyn Thomas

A nice answer but one that I would call "arty farty wiffle waffle" (actually I would use other words but that is a more polite version). Would it not have been nice to represent the development of technology by applying some basic physics and engineering and seeing if the damn thing worked first? I am pretty sure that is how we managed such a technological revolution. Interesting and succinct ideas stand for little in physics if they are clearly incorrect.

Category: Forex

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